PROJECT SUMMARY/ABSTRACT Bilateral cochlear implants (BI-CIs) improve speech understanding and sound localization, but it is unknown whether two ears afford any listening effort benefits to BI-CI listeners. The long term goal is to understand bin- aural (two-ear) benefits in hearing-impaired listeners so that hearing devices are designed not only to maximize speech perception but also minimize listening effort, a dimension of perception that is potentially important. The specific objective of this proposal is to evaluate changes in speech understanding and listening effort in BI-CI listeners for binaural tasks. The central hypothesis is that symmetrical ears improve binaural benefits, but asym- metrical ears limit these benefits. The approach is to combine behavioral measures of perception with pupillom- etry, an objective and physiological measure of listening effort, which has yet to be used as a tool to understand the benefits of two sound inputs in BI-CI listeners. The rationale is that consideration of listening effort and speech perception together can give a more complete picture of real-world listening. Binaural benefits to speech perception and listening effort will be explored in two aims: 1) to determine the extent to which asymmetrical inputs affect perception and listening effort in dichotic listening in BI-CI and normal-hearing listeners and 2) to measure the extent to which BI-CIs improve speech understanding and reduce listening effort with spatial sep- aration of talkers. The contribution of this research is expected to be knowledge of the benefit of binaural hearing to listening effort in BI-CI listeners. This contribution is significant because it is a first step in understanding listening effort and reducing it in the future, particularly in noisy environments, for hearing-impaired listeners. This proposal is innovative because it uses an objective physiologic technique ? pupillometry ? to measure listening effort in CI listeners, and combines binaural hearing and listening effort expertise to examine the ad- vantages of BI-CI listening. The PI of this Mentored Career Development Award is an Au.D.-Ph.D. postdoctoral researcher at the University of Maryland-College Park. The PI will acquire expertise in binaural hearing and listening effort, increase proficiency in the study of CI listeners and the use of CI simulations, develop program- ming skills to design auditory experiments and simulate sound locations, and learn advanced statistical methods under this award. Other training activities include coursework in statistical methods, on-campus seminars, formal training in grant writing, and presenting research at professional meetings. The PI has assembled an interdisci- plinary team of mentors who are experts in the PI?s areas of interest. This mentorship and the mentee?s strong psychoacoustics background will prepare the PI to reach the long-term goals of attaining a tenure-track faculty position and developing an independent, R01-funded research program as a clinician-scientist, focused on im- proving the hearing of individuals with hearing loss in noisy environments.